Analysis of field oriented controlled AC drive fed by a back-to-back three level NPC converter

This paper presents an extensive simulation study of the field oriented control application to the instantaneous power control of Electric Grid and Induction Motor Drive both connected via back-to-back PWM Active Front End Converter. The machine rated at 1.6 MW for conveyor application is fed from a 3.3 kV line voltage synthesized using a 3-level Neutral Point Clamped (NPC) Inverter which is interfaced to the 3.3 kV mains via 3-level NPC rectifier acting as a sinusoidal front end so that bi-directional power flow can be achieved. The performance of designed controllers has been evaluated on the basis of transient response behavior, settling time and peak time against theoretical values. It was found that the controllers responded with high overshoots and slower settling times contrary to the theoretical calculated values of the controller performance parameters. This paper investigates and identifies the variations in simulated and theoretical results of controller performance parameters from the root locus sketch of open loop and closed loop responses of the respective controllers. The simulations have been carried out in PLECS software using real system parameters.